The present invention relates to apparatus and methods for creating ultrasonic bonds in a web or webs, and/or in discrete workpiece segments, optionally in combination with a web or webs, using ultrasonic bonding apparatus. The invention more particularly concerns apparatus and methods for ultrasonically bonding a web or webs, and/or discrete workpiece segments, optionally in combination with a web or webs, using a rotary ultrasonic horn and a rotary anvil.
Bond strength, where a rotary ultrasonic horn and a rotary anvil are used to bond webs, or discrete workpiece segments is dependent on a variety of factors including horn frequency, horn amplitude, dwell time in the nip, bond pattern, and nip loading. More specifically, the consistency and quality of the bond when using such rotary bonding techniques is significantly dependent on the consistency of the force exerted on the web by the combination of the anvil roll and the rotary ultrasonic horn; the time during which the web is being pressed in the constrictive nip which is dependent in part on the operating speed at the nip; and the nature of the materials being bonded. The consistency and quality of the bonds are also dependent on the frequency and amplitude of the vibrations of the ultrasonic horn.
Consistency and quality of bonds when using conventional rotary ultrasonic bonding methods and apparatus have been particularly variable where the desired bond pattern is intermittently imposed on the material passing through the bonding nip because the nip pressures inherently change in concert with the intermittent nature of the bonding operation.
When nip loading is excessive, so much energy may be applied to the materials being bonded as to burn through or otherwise excessively soften the materials being bonded, as well as to apply so much pressure to the softened materials that the bonds so formed may be weak, and/or may be uncomfortably harsh to the touch of a wearer""s skin. In the alternative, excessive loading can physically damage, as by tearing, the material being bonded. Additionally, excessive loading can increase wear or coining and thus damage the ultrasonic horn.
In the past, control of the nip force has evolved from constant force to fixed interference. More specifically, early practice in the art of ultrasonic bonding was to force an anvil against a horn with a fixed, defined load. The anvil rode on the horn much like a train wheel runs on a rail. The force applied was substantially constant regardless of the presence or absence of material in the nip. The constant force of the fixed load design at high force levels tended to cause rapid horn wear.
The next step in the evolution of ultrasonic bonding was to load the anvil roll with high force against a fixed stop and to use the stop to establish interference. In this design, the stop drew a relatively high fraction of the load until material entered the nip; at that point, the greater interference caused by the material drew more of the load as the stop load diminished.
A need exists to develop apparatus and methods for loading a nip to a known force rather than loading to a fixed interference. Similarly, a need exists to develop apparatus and methods for loading a nip including measuring and adjusting a nip load as a direct reading of force rather than as an inferred value from a change in interference.
It is another object of this invention to provide ultrasonic bonding apparatus and methods wherein the bonding apparatus transmits a real-time ongoing and dynamic signal output to apparatus which is designed and configured to automatically adjust nip loading toward a known target load, without ongoing real-time human intervention.
It is yet another object of this invention to provide bonding apparatus and methods wherein a portion of the bonding apparatus can be automatically raised or lowered in response to detected nip loading output until the force applied to the respective portion of bonding apparatus results in desired ultrasonic bond-creating pressure in the nip.
In a first family of embodiments, the invention comprehends ultrasonic bonding apparatus for creating ultrasonic bonds in sequentially advancing workpiece segments, in a nip defined by a rotary ultrasonic horn mounted for rotation about a first axis, and a rotary anvil roll mounted for rotation about a second axis substantially aligned with the first axis. The anvil roll comprises a width, a circumference, and a bonding portion disposed about at least a portion of the circumference. The ultrasonic bonding apparatus comprises support structure comprising anvil support apparatus and the horn support apparatus. The anvil support apparatus is connected to the anvil roll, and horn support apparatus is connected to the ultrasonic horn. The support structure supports the bonding apparatus from an underlying support. The anvil support apparatus comprises an anvil moving assembly for moving the anvil roll into contact with the ultrasonic horn, and for moving the anvil roll out of contact with the ultrasonic horn. Closed loop control apparatus is connected to one of the anvil support apparatus and the horn support apparatus. The closed loop control apparatus comprises a programmable logic controller, a load cell, and an adjustor. The ultrasonic horn and the anvil roll collectively are mounted and configured such that the ultrasonic horn and the anvil roll can be brought together to define the nip therebetween, wherein the anvil roll and the ultrasonic horn can rotate in common with movement of workpiece segments through the nip. Information output from the load cell triggers the closed loop control apparatus through the programmable logic computer and the adjustor to move the one of the anvil support apparatus and the horn support apparatus toward and away from the other of the anvil support apparatus and the horn support apparatus in automatic and dynamic response to the information output from the load cell, thereby regulating pressure in the nip with ongoing real-time adjustments to distance between the anvil support apparatus and the horn support apparatus without real-time operator intervention.
In preferred embodiments, the load cell is arranged and configured to measure representative nip loads, thereby to define forces generated between the ultrasonic horn and the anvil roll.
In some embodiments, the adjustor comprises a servo motor.
In some embodiments, the invention comprises a load cell conditioner connected to the load cell. The load cell conditioner functions to amplify output from the load cell.
Preferred embodiments can include a back-up roll juxtaposed adjacent the ultrasonic horn, opposite the anvil roll, wherein the back-up roll engages an outer surface of the ultrasonic horn at an engagement locus in alignment with a line extending through extensions of the first and second axes.
In some embodiments, the invention includes a second adjustor mounted and configured for adjusting a height of the back-up roll, and thus generally defining a limit to movement of the ultrasonic horn away from the anvil roll.
In some embodiments, the closed loop control apparatus is connected to the horn support apparatus.
In other embodiments, the closed loop control apparatus is connected to the anvil support apparatus.
In some embodiments, the anvil moving assembly defines a limit to travel of the anvil support apparatus away from the horn support apparatus, thus defining a limitation to withdrawal of the anvil roll from the nip.
In some embodiments, the invention includes first and second support rolls releasably supporting opposing sides of an outer surface of the ultrasonic horn. Axes of the first and second support rolls can be positioned lower than the axis of the ultrasonic horn, whereby urging the first and second support rolls inwardly against the outer surface of the ultrasonic horn lifts the ultrasonic horn upwardly against the back-up roll.
In some embodiments, the invention includes drawing apparatus, capable of drawing the workpiece segments through the bonding apparatus, across the anvil roll, and thus through the nip defined between the anvil roll and the ultrasonic horn, at a threading speed of at least about 40 feet per minute, preferably at a speed of at least about 600 feet per minute, more preferably at a speed of at least about 1000 feet per minute.
In preferred embodiments, the support structure is sufficiently rigid that the ultrasonic horn and the anvil roll can be brought together with deflection levels of the horn support apparatus and the anvil support apparatus, in combination, being no more than about 0.003 inch in combination with defining sufficient nip pressure to develop ultrasonic bonds in the workpiece segments passing through the nip. Deflection is calculated using the formula, d=(Fl3)/3EI, wherein xe2x80x9cFxe2x80x9d represents the force expressed in the nip, xe2x80x9cIxe2x80x9d represents the length of the support structure, xe2x80x9cExe2x80x9d represents the modulus of elasticity of the material comprising the support structure, and xe2x80x9cIxe2x80x9d represents the moment of inertia for the cross-sectional area of the support structure. The moment of inertia for a support structure having a solid rectangular cross-section is calculated using the formula, I=(bh3)/12, wherein xe2x80x9cbxe2x80x9d represents the length of the base of the support structure, and xe2x80x9chxe2x80x9d represents the height of the support structure. The moment of inertia for a support structure having a solid circular cross-section is calculated using the formula, I=(nd4)/64, wherein xe2x80x9cdxe2x80x9d represents the diameter the circular support structure.
In a second family of embodiments, the invention comprehends closed loop control apparatus for managing pressure generated in a nip. The nip is defined between a rotary ultrasonic horn mounted for rotation about a first axis and an anvil roll mounted for rotation about a second axis, substantially aligned with the first axis. The anvil roll is mounted to support structure by anvil support apparatus, and the ultrasonic horn is mounted to the support structure by horn support apparatus. The closed loop control apparatus comprises a load cell, a programmable logic controller, and an adjustor. The load cell is connected to one of the anvil support apparatus and the horn support apparatus. The load cell quantifies force representative of pressure being generated in the nip. The programmable logic controller is connected to the load cell and to the adjustor, for communication with the load cell and the adjustor. The adjustor is mounted in adjusting relationship with the anvil support apparatus.
In preferred embodiments, the closed loop control apparatus further comprises a strain gauge isolated transmitter converting force applied on the load cell into signal output.
The load cell preferably functions to transmit the signal output to the programmable logic controller.
In some embodiments, the anvil support apparatus can be raised or lowered by the adjustor in response to output of the load cell and the programmable logic controller until force applied to the anvil support apparatus results in desired ultrasonic bond-creating pressure in the nip.
The horn is preferably mounted from a horn support apparatus having a first end portion mounted to the support structure, and a second end portion remote from the first end portion, and disposed on a horn moving assembly.
In some embodiments, the closed loop control apparatus is operatively connected to the anvil support apparatus, and a second closed loop control apparatus is connected to the horn moving assembly, thereby providing a second control for managing pressure in the nip. The second closed loop control apparatus comprises a second adjustor mounted in adjusting relationship with the horn moving assembly, and a second load cell connected to one of the horn moving assembly and the second adjustor, and outputting information to a suitable programmable logic controller.
In a third family of embodiments, the invention comprehends a method of creating ultrasonic bonds in sequentially advancing workpiece segments. The method comprises passing the workpiece segments through a nip, activating ultrasonic energy in an ultrasonic horn at the nip, and thereby creating ultrasonic energy in workpiece segments passing through the nip. The nip is defined by a support structure comprising anvil support apparatus, horn support apparatus, and closed loop control apparatus. The anvil support apparatus supports an anvil roll mounted for rotation about a first axis. The horn support apparatus is connected to and supports a rotary ultrasonic horn mounted for rotation about a second axis, substantially aligned with the first axis. The anvil support apparatus comprises an anvil moving assembly for moving the anvil roll into contact with the ultrasonic horn, and for moving the anvil roll out of contact with the ultrasonic horn. The closed loop control apparatus is connected to one of the anvil support apparatus and the horn support apparatus, and comprises a programmable logic controller, a load cell, and an adjustor. The method also includes rotating the ultrasonic horn and the anvil roll in common with movement of the workpiece segments through the nip, thereby applying pressure to the workpiece segments at the nip and correspondingly creating ultrasonic bonds in the workpiece segments passing through the nip.
In preferred embodiments, the method includes sensing nip loads using the load cell, the nip loads representing forces expressed between the ultrasonic horn and the anvil roll at the nip.
In some embodiments, the method includes employing the horn support apparatus and the anvil support apparatus, collectively, thereby to define a set-point target nip pressure of at least about 400 pounds per inch width of the nip, the nip having a width defined between the ultrasonic horn and the anvil roll.
In some embodiments, the method includes initiating adjustment to the anvil moving assembly when nip load deviates from a target nip load by at least about 10 pounds per inch width of the nip.
In some embodiments, the method includes adjusting the anvil moving assembly when loading in the nip corresponding to a bonding portion of the anvil roll varies by more than about 10 pounds per inch width of the nip from the target nip loading.
In some embodiments, the method includes connecting the closed loop control apparatus to the horn support apparatus.
In other embodiments, the method includes connecting the closed loop control apparatus to the anvil support apparatus. In yet other embodiments, the method includes managing pressure in the nip by employing a second closed loop control apparatus connected to the horn support apparatus in combination with the closed loop control which is connected to the anvil support apparatus.
In preferred embodiments, the method includes processing information output from the load cell in the programmable logic controller and correspondingly raising and lowering one or both of the anvil moving assembly or the horn support apparatus, thereby regulating the pressure in the nip.
Preferred embodiments of the method comprise applying first and second support rolls to sides of the ultrasonic horn and moving the ultrasonic horn into engagement with a back-up roll aligned with extensions of the first and second axes such that the first and second support rolls, in combination with the back-up roll, define a fixed location of operation of the ultrasonic horn.
In preferred embodiments, the bringing of the anvil roll and the ultrasonic horn together comprises lifting the anvil roll, thereby to bring the anvil roll into engaging relationship with the ultrasonic horn.
Preferred embodiments generally include limiting downward movement of the anvil moving assembly and thereby preventing disengagement of drive apparatus which transmits drive power between the anvil support apparatus and the horn support apparatus.
In some embodiments, the method includes adjusting height of the back-up roll and thereby controlling the location of operation of the ultrasonic horn.
In some embodiments, the method also comprises releasing the support rolls, causing the horn to drop out of engagement with the back-up roll, and subsequently re-engaging the support rolls with the ultrasonic horn, and thus bringing the ultrasonic horn back into engagement with the back-up roll, and thereby returning the ultrasonic horn to the defined location of operation of the ultrasonic horn.
In preferred embodiments, the method includes using the load cell to measure, and to dynamically manage, nip loads expressed in the nip, in real time.
Preferred embodiments of the method also generally include urging the anvil support apparatus, and the horn support apparatus together, wherein the anvil support apparatus and the horn support apparatus, collectively, are sufficiently rigid that the ultrasonic horn and the anvil roll can be brought together with deflection levels of the horn support apparatus and the anvil support apparatus being no more than about 0.003 inch in combination with defining sufficient nip pressure to develop ultrasonic bonds in the workpiece segments passing through the nip.
In a fourth family of embodiments, the invention comprehends a method of managing and regulating pressure generated in a nip. The nip is defined between a rotary ultrasonic horn mounted on horn support apparatus, and an anvil roll mounted on anvil support apparatus. The anvil support apparatus is mounted to a support structure, and defines an adjustable anvil moving assembly. The horn is mounted in general alignment with the anvil roll to define the nip therebetween such that outer working surfaces of the ultrasonic horn and the anvil roll are generally defined in a common surface at the nip. The method comprises employing a load cell connected to one of the horn support apparatus and the anvil support apparatus, and thereby receiving and quantifying force representative of force expressed between the ultrasonic horn and the anvil roll at the nip. The method also comprises converting the force applied at the load cell into a communications signal output. The method additionally comprises transmitting the communications signal output to a programmable logic controller programmed to activate an adjustor. The method further comprises employing the adjustor to raise or lower the respective anvil support apparatus or horn support apparatus so as to adjust the force being expressed between the anvil roll and the ultrasonic horn at the nip to a desired bond-creating pressure.
In some embodiments, the method includes employing a target nip pressure of at least about 400 pounds per inch width of the nip.
In preferred embodiments, the method includes initiating adjustment of location of the respective anvil support apparatus or horn support apparatus when pressure in the nip deviates from the target nip pressure by a defined number of pounds per inch width of the nip.
Preferred embodiments generally include adjusting the location of the respective anvil support apparatus or horn support apparatus when pressure in the nip corresponding to a bonding portion of the anvil roll deviates from the target nip pressure by a defined number of pounds such as about 10 pounds per inch width of the nip.
In some embodiments, the method includes the horn support apparatus having a first end portion fixed to the support structure, and a second end portion remote from the first end portion, disposed on a horn moving assembly, the method including at least in part managing pressure in the nip by connecting closed loop control apparatus to the horn moving assembly.
In some embodiments, the method includes limiting downward movement of the anvil roll and thereby preventing disengagement of drive apparatus which transmits drive power between the anvil roll and the ultrasonic horn.